1. Field of Invention
The present invention relates generally to the field of communication protocols. More specifically, the present invention is related to transferring a ATM protocol over an Internet protocol.
2. Discussion of Prior Art
ATM, short for Asynchronous Transfer Mode, represents a network technology based on transferring data in cells of a fixed size. The cell used with ATM is relatively small (53 bytes) compared to units used with older technologies. The small, constant cell size allows ATM equipment to transmit video, audio, and computer data over the same network, and assure that no single type of data hogs the line.
Current implementations of ATM support data transfer rates of from 1.544 (T1) to 622 Mbps (megabits per second). This compares to a maximum of 1000 Mbps (GbETH) for Ethernet, the current technology used for most LANs.
Some people think that ATM holds the answer to the Internet bandwidth problem, but others are skeptical. ATM creates a fixed channel, or route, between two points whenever data transfer begins. This differs from TCP/IP, in which messages are divided into packets and each packet can take a different route from source to destination. This difference makes it easier to track and bill data usage across an ATM network, but it makes it less adaptable to sudden surges in network traffic.
When purchasing ATM service, you generally have a choice of four different types of service: Constant Bit Rate (CBR) specifies a fixed bit rate so that data is sent in a steady stream. This is analogous to a leased line. Variable Bit Rate (VBR) provides a specified throughput capacity but data is not sent evenly. This is a popular choice, however, for voice and video conferencing data. Unspecified Bit Rate (UBR) does not guarantee any throughput levels. This is used for applications, such as file transfer, that can tolerate delays. Available Bit Rate (ABR) provides a guaranteed minimum capacity but allows data to be bursted at higher capacities when the network is free.
The present communications revolution has been focused on the Internet and World Wide Web (WWW) with emphasis on the Internet protocol (IP). The prior art has failed to teach a viable solution to handling ATM (ATM) over Internet Protocol (IP).
Each of the below described references teach methods of interworking functioning (IWF) for differing protocols across various communication standards. However, none of the references provide or suggest the present invention method of ATM over IP.
The patent to Essigmann (5,850,391), assigned to Telefonaktiebolaget L M Ericsson, provides for a Shared Interworking Function Within a Mobile Telecommunications Network. Essigmann discloses a method and apparatus for communicating interworking function (IWF) control data between a mobile switching center (MSC) and a telecommunication node as illustrated in FIG. 5 (5,850,391). The serving MSC encapsulates the identified IWF control data into an optional parameter within an integrated service digital network user part (ISUP) signal. The MSC then transmits the ISUP signal encapsulating the IWF control data towards the telecommunications node.
The patent to St-Pierre et al. (5,901,352) provides for a System for Controlling Multiple Networks and Associated Services. This reference describes a system for enabling network convergence and interworking between multiple communication networks. FIG. 1 (5,901,352) illustrates telecommunication network (10) with mobile switching center (30) that includes interworking function (IWF) for providing communication over different protocols.
The patent to Bhalla et al. (5,949,773), assigned to Motorola, Inc., provides for a Method for Transferring a Data Signal in a Wireless Communications System. Disclosed is a system for transferring a data signal in a communication system. Source selection distribution unit (SDU) (248) in FIG. 3 (5,949,773) converts incoming data signal (107) to ATM switched virtual circuit (ATM SVC) protocol suitable for conversion by source interworking function (IWF) (214), thus eliminating the need for protocol conversion by source SDU (170).
The non-patent literature entitled, xe2x80x9cTrends for 1999: Interworking Between ATM and IP networksxe2x80x9d, Network World Fusion, Jan. 1, 1999 (www.nwfision.com) provides a brief look at IP traffic bound for a destination on a ATM network which gets concentrated to one or more sites. At these sites, routers (or a routing function) also know the IP addresses at the ends of the ATM PVC""s, this is for IP over ATM networks and not ATM over IP networks.
The patent to Pepe et al. (5,742,668), assigned to Bell Communications Research, Inc. provides for a personal internetwork over wireless or wire-line communication mediums.
Whatever the precise merits, features and advantages of the above cited references, none of them achieve or fulfills the purposes of the present invention. These and other objects are achieved by the detailed description that follows.
A system and method of implementing interworking function (IWF) between ATM and IP protocols and networks. The interworking function provides mapping and encapsulation functions necessary to ensure that service (protocols) provided to networks is kept unchanged. The present invention provides a ATM service specific convergence sublayer (ATM-SSCS) necessary to translate between the ATM layer and RTP/UDP/IP sublayer.